tbgrad.h Source File

00001 //
00002 // tbgrad.h --- definition of the abstract two-electron gradient builder
00003 //
00004 // Copyright (C) 1996 Limit Point Systems, Inc.
00005 //
00006 // Author: Edward Seidl <seidl@janed.com>
00007 // Maintainer: LPS
00008 //
00009 // This file is part of the SC Toolkit.
00010 //
00011 // The SC Toolkit is free software; you can redistribute it and/or modify
00012 // it under the terms of the GNU Library General Public License as published by
00013 // the Free Software Foundation; either version 2, or (at your option)
00014 // any later version.
00015 //
00016 // The SC Toolkit is distributed in the hope that it will be useful,
00017 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00018 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00019 // GNU Library General Public License for more details.
00020 //
00021 // You should have received a copy of the GNU Library General Public License
00022 // along with the SC Toolkit; see the file COPYING.LIB.  If not, write to
00023 // the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
00024 //
00025 // The U.S. Government is granted a limited license as per AL 91-7.
00026 //
00027 
00028 #ifndef _chemistry_qc_scf_tbgrad_h
00029 #define _chemistry_qc_scf_tbgrad_h
00030 
00031 #ifdef __GNUC__
00032 #pragma interface
00033 #endif
00034 
00035 #include <util/group/thread.h>
00036 
00037 namespace sc {
00038 
00039 template<class T>
00040 class TBGrad : public Thread {
00041   protected:
00042     T& contribution;
00043     double exchange_fraction;
00044 
00045   public:
00046     TBGrad(T&t, double ex = 1.0) : contribution(t), exchange_fraction(ex) {}
00047     virtual ~TBGrad() {}
00048 
00049     inline void set_scale(double& coulombscale, double& exchangescale,
00050                           int i, int j, int k, int l) const
00051     {
00052       double scale = 1.0;
00053 
00054       if ((i!=k)||(j!=l))
00055         scale *= 2.0;
00056 
00057       if (i!=j)
00058         scale *= 2.0;
00059 
00060       coulombscale = 0.5*scale;
00061       exchangescale = -0.25*scale * exchange_fraction;
00062 
00063       if (k!=l)
00064         coulombscale *= 2.0;
00065 
00066       if ((k!=l)&&(i==j))
00067         exchangescale *= 2.0;
00068     }
00069 };
00070 
00071 }
00072 
00073 #endif
00074 
00075 // Local Variables:
00076 // mode: c++
00077 // c-file-style: "ETS"
00078 // End: